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  1. #1
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    Exspansion Valves,



    Need some things clearly explaining to me, I can set the super heat up on a system with no problems but what I dont understand is a superheat chart when It says ''required superheat'' WET BULB TEMPERATURE and DRY BULB Temperature and the difference on the chart.

    Thanks



  2. #2
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    Re: Exspansion Valves,

    Is there some confusion in your requirements the super heat of refrigerant is "sensible heat" ie heat that changes the temperature of a substance.
    It appears you are referring to properties of air in a conditioned space.
    Please advise what you are looking for from this forum, there are many skilled techs that can assist you.
    Dry bulb and wet bulb temperatures when plotted on a psychometric chart will provide the properties of standard air at the plotted conditions.
    Location, United Kingdom

  3. #3
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    Re: Exspansion Valves,

    Hi NZPOMME.
    TX valve super heat is critical to any system performance, and has been well discussed on this site. do site seach on subject. Kueba web site, go to tools and there is a good explanation of TX superheat.

  4. #4
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    Re: Exspansion Valves,

    .

    Wet bulb and Dry bulb refer to humidity measurement for air,

    but there is Bubble point and Dew point or Liquid tempreature and Vapour temp.

    It has everything to do with Zeotropic refrigerants with a large temp glide.

    Take R407c for example... R407c has a 6 deg glide.

    That means it starts boiling and finishes boiling over a 6 degree range.

    The technical term is the saturation temperature.

    If water boils at 100 degC in an open pan then it has a saturation temp of 100 degC

    R407c saturates over a six degree range at any one given pressure.

    So if you measure the superheat at the liquid temp or Bubble point then that
    is the start of the glide process and it will take six degrees to fully turn to vapour at
    the Dew point.

    If you are setting the superheat setting to six degrees and measure the temp from the
    Bubble or liquid temp, then when the liquid boils off it will still be at the Dew point temp
    and therefore the risk of some liquid leaving the evaporator is possible.

    All the best

    coolrunnings

    .
    Last edited by cool runings; 20-11-2011 at 02:50 AM.

  5. #5
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    Re: Exspansion Valves,

    wet bulb and dry bulb is measurments of the air temp measured in degC
    superheat and subcooling is measured in degC but is referred to as K ( kelvin ) this is a temp difference this is so these temp do not get confused.
    ie if you have 5 degC superheat it would be 5K
    if your air off for argument sake was 5 degC it would be 5 degC

    a danfoss TX valve is factory set for 5k you should never really have to adjust your tx valve but most engineers are like magpies if its shinny they will steal it are mess about with it.
    Last edited by cold.man; 20-11-2011 at 01:37 AM.
    your only as good as your last job

  6. #6
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    Re: Exspansion Valves,

    cheers for your help, sorry if I havnt been clear enough, But I just wanted the basic explantion of wet/dry bulb, And when I was setting up a exspansion valve would I need to look at the chart to be more Accurate. As for doing searches Am new to the forum just getting use to it

  7. #7
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    Re: Exspansion Valves,

    Quote Originally Posted by NZPOMME View Post
    cheers for your help, sorry if I havnt been clear enough, But I just wanted the basic explantion of wet/dry bulb, And when I was setting up a exspansion valve would I need to look at the chart to be more Accurate. As for doing searches Am new to the forum just getting use to it
    See my reply above.

    I answered your question.

    All the best

    coolrunnings.

    .

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